The idea of artificially interfering with the planet’s ecology to slow down climate change has always been very contentious. Today, with climate change being an urgent challenge, it is creeping closer to being taken seriously. Here, we explore if the various types of geoengineering under consideration are too much of a risk to contemplate.
Climate change is a pressing issue that is driving a range of measures, including the current massive shift away from fossil fuels towards renewables. Yet progress so far on climate change has been largely unambitious, and there are increasing concerns that the climate may be losing its stability. The North Atlantic’s “conveyor belt” warm ocean current is showing signs of slowing, global average temperatures are experiencing an unprecedented uptick, and the polar vortex zone is becoming more erratic, sometimes bringing colder-than-usual air into higher latitudes.
A new sense of urgency is prompting the consideration of some highly contentious proposals.
Reflecting the heat
For years, some scientists have been discussing intervening in the Earth’s climate system via geoengineering, sometimes described as climate engineering. Much of this involves solar radiation modification (SRM), strategies for reducing the amount of solar radiation hitting the planet by enhancing its albedo (reflectivity) and reflecting this radiation back into space.
Sometimes the definition of geoengineering is extended to take in high-tech carbon sequestration via such techniques as carbon capture and storage (CCS), bioenergy with carbon capture and storage (BECCS), direct air capture and enhanced weathering. Then there is the “chemtrail” controversy, which is often perceived as a form of geoengineering that is already occurring at scale. If it is a real phenomenon, there appears to be a lack of evidence that its primary function relates to addressing climate change. The scope of this piece excludes both, and omits cloud seeding with chemicals such as silver iodide to encourage rain.
Climate engineering appears to have been first suggested in 1965, when US President Lyndon Johnson’s Science Advisory Committee raised it as an option. Perhaps more remarkable is that the American government privately saw a threat from climate change so many decades ago and that the report made no suggestions to cut emissions as a means of tackling the problem.
Today, broad-scale geoengineering is viewed as risky, with possible severe unforeseen consequences. Public support is low across a range of countries. Yet in recent years, the debate has shifted in favour of opening it up to consideration. This was underscored in March 2024, when the head of the US National Oceanic and Atmospheric Administration stated that work on understanding the effects of geoengineering was necessary, because these technologies would probably need to be deployed.
Stratospheric aerosol injection (SAI)
Stratospheric aerosol injection (SAI) involves spreading specific substances at high altitudes, often involving the use of helium balloons. It aims to mimic the planet-cooling effect from large volcanic eruptions, such as Mount Pinatubo in the Philippines, which is estimated to have lowered global temperatures by 0.5°C from 1991-1993. The Intergovernmental Panel on Climate Change (IPCC) has referred to “high agreement” that SAI could limit warming to below 1.5°C. On the downside, SAI has been acknowledged as a major risk to the ozone layer, and the use of sulfur could also cause acid rain. An estimated annual cost for pursuing SAI on a large scale is US$2.25 billion.
In 2022, in Baja California, Mexico, an American named Luke Iseman burnt a few grams of sulfur and transferred the resulting sulfur dioxide into a 2m helium weather balloon that was then released into the sky. Both items had recently been purchased from Amazon, as part of a shoestring-budget experiment carried out by start-up Make Sunsets, probably the first stratospheric solar geoengineering test anywhere in the world. No government permission had been sought, and the balloon was not tracked. The aim was for it to burst at altitude and discharge its tiny payload.
Mexico later prohibited solar geoengineering tests, prompting the company to relocate its activities to Nevada, USA, where dozens of further small balloon launches have occurred. Make Sunsets sells US$10 Cooling Credits carbon offsets to the public, which are based on the premise of 1g of material released into the stratosphere curbing one tonne of atmospheric carbon. The offset value of SAI is hard to calculate accurately, and the company’s online FAQs link has no details about the basis for arriving at this offset ratio.
Marine cloud brightening
Another technique called marine cloud brightening targets the thick stratocumulus clouds that are found over about 20 per cent of the tropical ocean, with a view to increasing their reflectivity. An idea is to utilise a fleet of unmanned, remotely controlled and wind-driven Flettner rotor vessels. These would spray very fine salt particles, collected from seawater, in a plume that would drift upwards.
In Australia, brightening trials have been conducted over the Great Barrier Reef since 2020 by a team from Southern Cross University as part of the Reef Restoration and Adaptation Program. The goal of this brightening project is to protect coral from dying due to the effects of temperature-driven coral bleaching events.
Ocean fertilisation
Geoengineers are also looking at ocean fertilisation, in which iron – and sometimes phosphorus or nitrogen – is released offshore in large quantities. The plan is to substantially boost the growth of carbon-sequestering phytoplankton – a selling point for this technique is a boost in the populations of fish that feed on these microscopic plants. Dimethyl sulfide emitted by ocean phytoplankton has the additional effect in the atmosphere of increasing cloud reflectivity. On the flipside, larger releases of dimethyl sulfide could globally reduce rainfall.
American entrepreneur Russ George aroused significant controversy in 2012 when he dumped 120 tonnes of iron sulfate and iron oxide off the coast of British Columbia without government approval. More recently, an American company called Oceanos has been active in this area, although it is focused on restoring ocean health rather than the CO2 issue.
The Mad Scientist fringe
Some other techniques are more speculative, weird and outlandish. such as a Silicon Valley non-profit called the Arctic Ice Project. The initiative aims to prevent sea ice loss by spreading a thin layer of tiny reflective glass beads in unspoilt environments. These are very fine, hollow, sand-like silica microspheres, less than the width of a human hair. The company believes that they will dissolve in the environment over time. Trials have involved spreading these spheres over ice-covered lakes in the Sierra Nevada mountains, Minnesota and Alaska. There are concerns that this intervention could affect the local food chain, and recent research concluded that it could have the opposite effect to the one desired, by accelerating melting when applied in snow conditions.
Two allied ideas involve injecting the ocean with micro-bubbles or spraying it with sea foam in order to make it more reflective. The bubbles would require the use of surfactants, and producing sea foam could involve gelling agents and cellulose ethers. The effects of these chemicals in the environment are a concern and increasing the albedo could negatively affect marine biodiversity.
Deploying large numbers of mirrors in space was first suggested as far back as 1923 by rocket scientist Hermann Oberth. Among the most sci-fi of geoengineering ideas, this has been given little serious attention because of its astronomical cost.
Shortcomings and risks
Scientists and environmentalists who have studied geoengineering have identified several issues that tend to apply across many of the proposals:
- To tangibly affect planetary temperatures, today’s small-scale trials would need to be scaled up massively, multiplying the inherent risks and environmental impacts.
- Risks from wide-scale geoengineering include effects on climate and weather, loss of biodiversity and undermining food security via measures such as reducing levels of light. The full ramifications are very hard to predict.
- The IPCC’s Sixth Assessment Report in 2023 noted critical knowledge gaps relating to SRM.
- Some measures would require large quantities of energy to deploy.
- For large-scale geoengineering, it may be very difficult to achieve an international consensus among countries that may be affected.
- Without sufficient oversight, it could be misused for geopolitical ends.
- Once a large-scale climate engineering measure has been initiated, it would be necessary for it to be maintained more or less indefinitely, regardless of the cost and difficulty involved. The reason is because discontinuing it would create a temperature spike called a “termination shock”. One study found that this could be up to four times greater than the warming caused by climate change itself.
Opponents and supporters
Mary Church, the geoengineering campaign manager of the Center for International Environmental Law (CIEL) would like to see solar geoengineering added to a list of things that are banned under international law, along with eugenics, human cloning and chemical weapons. In March 2024, Church was quoted as stating “Solar radiation modification technologies are dangerous and do not have any role to play in our common future. These technologies cannot tackle the root causes of the climate crisis and would instead enable major polluters to delay the urgent need to phase out fossil fuels.”
The strongest opposition has come from the ETC Group, via its Hands Off Mother Earth campaign, whose manifesto has been signed by 195 groups from 45 countries, including Friends of the Earth International. Its definition of geoengineering extends beyond SRM into some questionable high-tech avenues for carbon sequestration. Two main concerns include solar geoengineering as a possible weapon of war, and the risk of it disrupting the African and Asian monsoons.
More than 500 academics have signed an International Non-Use Agreement on Solar Geoengineering that has five simple demands, namely no public funding, no outdoor experiments, no patents, no deployment and no support from international institutions. Another 101 governments have signed a statement critical of the risks posed by marine climate engineering.
At the other pole, support is coming from some universities, scientists, tech nerds, philanthropists and billionaire entrepreneurs. Bill Gates alone had funded US$4.5 million worth of geoengineering research by 2010. Adherents include people who think climate change can be resolved using technology. The gestalt here is generally high-tech, expensive and top-down, rather than local and grassroots.
A regulatory framework
Since 2010, the world has been subject to a de facto moratorium on large-scale climate engineering that was instituted during a UN biodiversity conference. On the downside, this moratorium is hampered by somewhat vague language.
At the 2024 United Nations Environment Assembly, it was revealed that those countries most amenable to geoengineering were generally the richest, especially the US, Japan and Saudi Arabia, while most of the opposition came from the Global South. Switzerland put forward a motion advocating the creation of an expert group on SRM, but it was later withdrawn due to a lack of consensus.
The issue of creating a regulatory framework is a fraught one, with concerns that it would undermine the current moratorium and facilitate a large-scale roll-out. Another perspective is that such a framework would ensure that any future activities do not occur under lax policies or in a regulatory vacuum.
Some better alternatives
It is acknowledged that the large-scale deployment of climate engineering would be a desperate measure to buy time for steep emissions reductions to take place, when time has otherwise run out. It is not a solution to the climate crisis, or a substitute for the painful business of cutting emissions. Geoengineering fails to tackle the allied climate-related issues of ocean acidification and air pollution. Project Drawdown, a scientifically based resource for climate change solutions, does not feature any type of climate engineering in its list of key measures.
Arguably, a meaningful response to climate change would go beyond the focus on renewables and electric cars and into the more challenging realms of ending economic growth, limiting consumerism and curbing population growth.
Current scientific consensus is that carbon-negative measures will be needed to prevent climate overshoot. Environmentally benign options include regenerative farming, boosting the carbon uptake of soil by increasing its organic matter, small-scale biochar production, reforestation in tropical zones and carbon-negative construction using materials such as hemp, straw or bamboo.
Other ways in which albedo enhancement can be achieved on a limited scale is through roofs that are a light colour or have a special reflective roof coating added. This bounces back the sun and reduces energy use in the dwellings involved. In the Los Angeles area, a similar effect is being created with roads that have been painted a light grey instead of being the normal black colour. Meanwhile, cover crops and vegetation both perform better than bare soil in increasing the planet’s albedo.
The remaining question is whether such measures, taken together, can cut emissions sufficiently faster than geoengineering is unnecessary.